L-(+)-.beta.-hydroxyisobutyric acid is used in the preparation of epi-captopril, which has the structure ##STR1## an angiotensin-converting enzyme inhibitor useful in the treatment of hypertension. It may also be used in preparing the monomer .alpha.-methacrylic acid which is used in preparing polyesters and other synthetic polymers.
Until now, L-(+)-.beta.-hydroxyisobutyric acid has been prepared through the use of fermentation techniques. For example, U.S. Pat. No. 3,553,081 to Goodhue et al discloses that L(+)-beta-hydroxyalkanoic acid can be obtained by oxidizing an alkanoic acid containing 4 to 6 carbon atoms and at least one hydrogen on the beta-carbon atom, such as isobutyric acid, isovaleric acid and isocaproic acid with a microorganism selected from the group consisting of Pseudomonas putida, Pseudomonas fluorescens, Arthrobacter oxydans, Arthrobacter crystallopietes and Mycobacterium.
Japanese Kokai Pat. No. SHO 57 [1982] 65192 discloses a method of preparing L(+)-.beta.-hydroxyisobutyric acid by employing microorganisms that have the ability to convert isobutyric acid or methacrylic acid or a mixture of the two to L-(+)-.beta.-hydroxyisobutyric acid, such as microorganisms belonging to the genera Bullera, Candida, Cryptococcus, Debaryomyces, Dekkera, Hanseniaspora, Pachysolen, Pichia, Rhodosporidium, Rhodotorula, Saccharomyces, Schizosaccharomyces, Schwanniomyces, Sporobolomyces, Torulopsis, Trichosporon, Hansenula, Sporidiobolus, Nocardia, Streptomyces, Endomyces, Geotrichum, Helicostylum, Mucor, Paecilomyces, Fusarium, Bacillus, Brevibacterium, Corynebacterium, Enterobacter, Micrococcus, Sarcina and Kloeckera.